Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandrosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.
Figure 5. Mitochondrial cholesterol transport and metabolism machinery . The mitochondrial cholesterol import and metabolism machinery are shown, demarcated by red (transduceosome) and blue (metabolon) dashed lines, respectively. The transduceosome contains cytoplasmic (StAR, ACBD3, DBI, and PRKARI; colored blue), OMM (VDAC and TSPO; colored green), and IMM (ATAD3A; colored red) components which assemble in response to hormonal stimulation and transduce the resultant cAMP signal to the mitochondria for cholesterol import. It is important to note, however, that molecular details of cholesterol import are still lacking. Once cholesterol is imported into the mitochondria, the IMM metabolon (CYP11A1, FDX, and FDXR; colored red) metabolizes cholesterol to pregnenolone, the precursor to all other steroids, including adrenal glucocorticoids and mineralocorticoids.